The present invention relates to a belt unit and an image forming apparatus having the belt unit.
In a conventional image forming apparatus such as a printer, a copier, a facsimile, and the likes, a charge roller charges a surface of a photosensitive drum, and an LED (Light Emitting Diode) head exposes the surface of the photosensitive drum to form a static latent image thereon. Then, a developing roller attaches a thin layer of toner to the static latent image through static electricity, thereby forming a toner image. A transfer roller transfers the toner image to a sheet, and a fixing device fixes the toner image to the sheet, thereby forming an image on the sheet. After the transfer roller transfers the toner image to the sheet, a cleaning device removes toner remaining on the photosensitive drum.
In the printer described above, image forming units are disposed for forming toner images in colors, and the sheet is transported along the image forming units. To this end, a belt unit is disposed along the image forming units. The belt unit includes a drive roller, an idle roller, and a transfer belt extended between the drive roller and the idle roller. When the drive roller rotates, the transfer belt moves, thereby transporting the sheet. Further, a tension mechanism is disposed for applying a tensional force or tension to the transfer belt (refer to Patent Reference).
Patent Reference: Japan Patent Publication No. 2002-60039